A device for moving tools along a circular trajectory

Abstract: This device is a piece of apparatus which allows the user to execute circumferences with large radii, including radii longer than the apparatus itself, without the need for a support at the centre of curvature. It is capable of making an arc of circumference with a radius of several metres on a small sheet of paper (A4 for example) without the need for any support outside the area of the paper. It is made up fundamentally of two knurled wheels (1 and 2) linked by an axis (4) which act as moveable supports for a third point consisting of a ball (3) which is able to move in all directions. As it moves the apparatus pulls along a pencil, pen or saw to draw or cut the circumference. The radius of the circumference can be varied either by moving the bracket (5) for the pencil, pen or saw along a graduated scale (6) attached to the body of the device (7) or, for greater differences, by moving the wheels closer together or further apart. The device may also have groups of several wheels on the same axis which can be moved to allow a greater range of radii to be obtained.

Description: A device for moving tools along a circular trajectory is an item of apparatus which allows the user to execute circumferences and arcs of circumferences with radii of any length, including radii longer than the apparatus itself, without needing to place a fixed point in the centre of the circle. Such device is known from FR-A-2575420. It is capable of making an arc of circumference with a radius of several metres on a small sheet of paper (A4 for example) without the need for any support outside the area of the paper. Used in conjunction with any kind of cutting equipment (a fret saw for example) it makes it possible to cut a circle immediately, without the need for a central attachment. Positioned for a radius of infinite length, it does away with the need for a parallel guide, and can moreover continue in any direction. The device according to claim 1 is made up fundamentally of three moveable points of support, two of which are linked by an axis and the third of which consists of a moving ball which is pulled in the direction of movement of the first two. This last serves to keep the device stable, preventing large variations in the pressure exerted on the pencil or pen or, in the case of cutting tools, keeping the blade at a constant height. The two connected points of support take the form of two wheels which are knurled so as better to grip the paper. Where electric cutting tools are to be used this knurling must be deeper, to prevent the vibrations of the tool pushing the device off course. It is essentially the following which makes it possible to trace an arc of circumference of a certain radius: 1. The two wheels connected by an axis have different diameters, so that when they roll they have a conical motion, acting like two planes of a frustum perpendicular to the axis. 2. The wheels can be moved along the axis and fixed in place so that they are closer together or further apart, in such a way as to modify the frustum that they define, and thus change the radius of the curve that they describe. 3. There can be more than two wheels, with some attached to others, for example by means of screws, with at least one in each set capable of being fixed to the axis to prevent the set from rolling. Only the two wheels with the greatest diameter in each set rest on the work surface, so that by moving one or more wheel from one set towards another, and moving the sets closer or further apart by sliding one of them along the scale, it is possible to obtain a continuous range of radii.

Claims: A device for moving tools along a circular trajectory, comprising; a body with an axis (4) to which are attached two wheels (1, 2) of different diameters, the body allowing the device to roll ín a circle when the two wheels (1, 2) rest on a level surface, and a bracket (5) for a writing implement, for example a pen or a cutting tool, for example an electric saw, the position of which can be adjusted along the edge of the body by way of a first graduated scale (6), to allow trajectories of different radii to be drawn or cut, the wheels (1, 2) being movable along the axis (4) to different positions, so as to alter the range of radii that can be obtained by sliding the bracket (5) along the first scale (6). characterised in that the body has a third, spherical point of support (3) which rolls in any direction to enable the device to remain in a stable position and in that a second scale is marked on the axis. A device according to claim 1 comprising several wheels of different diameters, arranged in two groups, which are capable of being attached to the axis (4) and to each other, such that the wheel of greatest diameter in each group rests on the work surface, and by moving one or more from one group to the other it is possibie to vary the wheel which is in contact with the surface, thus extending the range of radii that can be drawn.

Inventors: CANDEIAS JOAQUIM ANTONIO ABRAN, CANDEIAS, JOAQUIM ANTONIO ABRANTES
Applicants: CANDEIAS JOAQUIM ANTONIO ABRAN, CANDEIAS, JOAQUIM ANTONIO ABRANTES
Application year: 1994
Main classification: B43L9
IPC codes: B43L9, B26B29